Observation of resonant doublet and variable finesse in a tabletop meter-scale linear three-mirror cavity

TL;DR

This paper reports the experimental observation of resonant doublet and variable finesse in a meter-scale linear three-mirror cavity, which are promising features for improving gravitational-wave detectors.

Contribution

First experimental demonstration of resonance peak splitting and variable finesse in a linear three-mirror cavity, confirming theoretical predictions.

Findings

Observation of resonant doublet in the cavity

Demonstration of variable finesse control

Implications for gravitational-wave detector sensitivity

Abstract

Fabry-Perot cavities are widely used in current gravitational-wave detectors. In particular, they play a key role in frequency-dependent squeezing systems, enabling broadband quantum noise reduction. However, their ability to precisely control squeezing properties may be insufficient for the next generation of detectors. In this context, theoretical studies on linear three-mirror cavities have revealed promising features, such as resonance peak splitting and their equivalence to two-mirror cavities with variable finesse. In this paper, we report experimental observations of both the resonant doublet and variable finesse using a meter-scale implementation of a linear three-mirror cavity.